In general, this invention relates to methods for winding into an electrochemical cell, a plurality of flexible strip members as well as electrochemical cells produced by such methods. More particularly, this invention relates to a method for winding into an electrochemical cell, a plurality of flexible strip members each having a leading end portion, that includes bringing a first generally flat surface of a first arbor half toward a second generally flat surface of a second arbor half along a direction generally perpendicular to the first generally flat surface, to capture at least a portion of the leading end portions therebetween, and rotating the first and second arbor halves with the leading end portions captured, to wrap the leading end portions around a first curvilinear driving surface of the first arbor half; and it relates to an electrochemical cell, produced by such a method, having a central opening that extends the length of the axis of the cell and is circumscribed by a first conducting flexible plate of the cell.
Various techniques and apparatuses for spirally winding electrochemical cells into a generally cylindrical "jelly roll" configuration are known. Typically, a mandrel or split arbor is used to wind the strip-like components of the electrochemical cells. These mandrels or split arbors are either solid with grooves or notched lands, clothespin shaped, or split into two separate halves which slide together (concurrently or at different times) along the same direction to grab and hold the strip-like components for winding. Even if the two arbor halves are tapered such that their tips have the smallest cross-section (see FIG. 6 of U.S. Pat. No. 4,203,206 and FIG. 1 of U.S. Pat. No. 4,559,700), this sliding motion often causes the strip-like components to be pushed-out of, or to buckle between, the arbor halves. Additionally, since the known split arbors slide together, the strip-like cell components must be either (1) fed between the arbor halves in a "pre-sandwiched" form or (2) positioned against an arbor half and held tightly together by some means as shown in FIG. 7C in U.S. Pat. Nos. 4,203,206 and 4,360,140. This adds another step to the winding process and adds another mechanism to the winding apparatus, thus slowing down, adding costs to, and increasing the complexity of the winding process.
Repeatability of high-quality wound cells is low for the known winding processes and apparatuses. In particular, as the arbor halves are pulled from a wound jelly roll, oftentimes the inside windings pull out with the arbor halves causing "spiralling" of the cell. These cells must be scrapped. Furthermore, it is desirable to configure the cells so that cells can easily and quickly be filled with a maximum specified amount of electrolyte. Since cells are usually filled with electrolyte through their centers, it is difficult to easily and quickly fill cell configurations produced by known jelly roll winding processes because the centers of these cell configurations are "filled" with separator material (see FIGS. 7D and 7E of U.S. Pat. Nos. 4,203,206 and 4,360,140) or jelly roll components (see FIG. 15 of U.S. Pat. No. 2,506,314 or FIGS. 24 and 25 of U.S. Pat. No. 2,340,340). A desirable electrochemical cell configuration can be produced by grabbing and winding the leading ends or edges of the malleable conducting plates or electrodes to be wound. However, known cell winding processes and apparatuses do not grab and hold the leading ends or edges of the malleable conducting plates or electrodes because this will cause the leading ends to crack. Therefore, the known processes include methods, where, only the separator strips are grabbed and wound prior to introducing any malleable conducting plates or electrodes (see FIG. 7E of U.S. Pat. Nos. 4,203,206 and 4,360,140).
It is a primary object of this invention to provide a method for winding an electrochemical cell capable of efficiently producing quality cells. It is another object to produce an electrochemical cell by such a method having a configuration that is less costly to make and may extend the life of the cell.